Lapping device



Patented Feb. 17, 1931 CONRAD F. BIRGBAUER, OF DETROIT, MICHIGAN LAPPING DEVICE Application filed March 15, 1930. Serial No. 436,190.

The main objects of this invention are to provide improved lapping and grinding de-- vices on which granular abrasives such" as diamond dust are used; to provide a device of this kind which has a plurality of closely held together convolutions betweenwhich abrasive material is confined; to provide abrasive material between adjacent convolutions which have aligned corresponding surfaces forming a working surface infconjunction withthe abrasive material; to provide releasable means for retaining said convolutions in a compressed position'so as to allow the convolutions to be expanded for renewing the deposits of abrasive material;'to provide films of abrasive material which extend inwardly from the working surface of the device a substantial distance so as to maintain a uniform cutting capacity as the work ing surface wears during operation; and to provide deposits of abrasive material in crevices between adjacent turns of a substantially soft, metal coil so that as the abrasive material is dislodged during operation it is embedded in the metal.

An illustrative embodiment of my inven-' tion is shown in the accompanying drawing, in WhlCl'l- Fig. 1 is a side elevation of a lap embodying my invention.

Fig. 2 is a side elevation, partly in section, showing part of the lapping device in an expandedposition.

Fig. 3 is a central, vertical section showing a modified form of my invention.

Fig. 4 is a central section showing a further development of my invention Fig. 5 is a plan View showing a part of the device illustrated in Fig. 4 in an expanded position.

.Fig. 6 is a fragmentary section taken on the line 66 of Fig. 5. 1

In theform shown,.the lap has a shank 1 having a driving tang 2 on one'end which may be engaged between jaws of a rotary drive mechanism (not shown). Formed on the other end of the shank 1 is an enlarged cylindrical head 3 having a substantially flat radial extremity or shoulder 4, beyond which a stem 5 of reduced diameter extends.v Seatwhich ed on the stem 5 is a helical coil 6 which has a centralpassage 7 for receiving the stem 5. The diameter of the central passage 7 may be slightly greater than the diameter of the stem 5 and the outer diameter of the coil 6 is preferably greater than the diameter of the cylindrical head 3, thus causing the outer periphery of the coil to protrude the periphery of-the head 3.

The helical coil 6 is preferably formed of spring bronze or other suitable resilient material which is somewhat ductile, such as aluminum, copper and brass. .Ca'st iron, steel, or other comparatively hard metals may be employed for this purpose if desired.

This coil is formed of a flat bar or strip of metal which is wrapped helically 'on an arbor with the .outer surfaces of each convolution in alignment with each other. The pitches of the convolutions are substantially uniform and the sides. of the convolutions may be finished so as to allow the adjacent sides thereof to be drawn into close proximity of each other when the coil is compressed.

A film of abrasive material 8-, preferably diamond dust, is provided between adjacent convolutions of the coil 6. Any other suitable material such as carborundum or emery of granular form may be used. The abrasive, in a vehicle such as oil, is preferably smeared or otherwise applied upon corresponding sides of all of the convolutions while the coil is in an xpanded position. Glue or other adhesive substances may be used in place of the 'oil to secure the abrasive in place while the device is being assembled. The coil 6 is then drawn down or compressed to the shape bedded in such surfaces.

In the form shown in Fig. 3, the lapping toolcomprises a shank 1 having a head 3' which is provided with a central a erture in a stem or bolt 5- is mounte Seated on the bolt 5 is'a helical coil 6 uavin a film ofabrasive material 8" between its a jacent 1 0 convolutions. The coil 6 is releasabl held in a com ressed position between t e extremity o the head 3' and a washer 10 by a bolt 11. When the bolt 11 is removed the spring 6 expands permitting a new film or deposit of abrasive material to be applied on the side of the convolution.

In the form of my invention shown in Figs. 4, 5 and 6, a flat spiral coil 12, preferably of spring bronze, is seated in a cylindrical cup 13 which is mounted on the end of a shank l l by a screw 15 having a countersunken head. The screw 15 extends centrally through the coil 12, retaining the latter under compression within the en 13. A film of abrasive material is located etween adj acent convolutions of the coil and the abrasive material is exposed at the ends of the convolutions which are arranged substantially'in alignment with each other.

In each form of my invention, the aligned outer surfaces of the convolutions and the exposed areas of the abrasive films provide working surfaces which have fast cutting capacities. When the coils are formed of comparatively soft metal, the particles of abrasive which are dislodged from the crevices between the adjacent convolutions become embedded in the exposed surfaces thereof and remain in a useful position. It may here be noted that in some instances grains or particles of abrasive independent of the films between the turns, may be rolled or otherwise worked into the cutting surface of the device to enhance its euttlng value.

Although but several specific embodiments of this invention have been herein shown and described, it will be understood that various changes including the size, shape and arrangement of parts may be made without departing from the spirit of my invention, and it is not my intention to limit its scope other than by the terms of the appended claims.

I claim:

1. lapping tool comprising a coil of substantlally rigid material, and abrasive substalnce between adjacent convolutions of said 001 2. A lapping tool comprising a coil of substantially soft metal material, and diamond dust clamped between adjacent convolutions of said coil.

3. A lapping device comprising a plurality of convolutions of metal each having a surface in alignment with a corresponding surface of each of the other convolutions, and abrasive material between adjacent convolutions and exposed at said aligned surfaces.

4. A lapping device comprising a plurality of convolutions of metal each having a surface in alignment with a corresponding surface of each of the other convolutions, and a film comprising granular abrasivematerial and a vehicle between adjacent convolutions and exposed at said aligned surfaces.

5. A lapping tool comprising a coil of metal material, an abrasive substance between adjacent convolutions of said coil, and means engaging the respectively opposite ends of said coil for retaining the same under compression.

6. A tool of the class described comprising a shank, a support on said shank, a metal strip helically formed about said support, and abrasive material confined between adjacent turns of said metal strip.

7. A tool of the class described comprising a shank, a support on said shank, a metal strip coiled on said support, and abrasive material confined between adjacent turns of said metal strip.

j 8. A tool of the class described comprising a shank adapted to rotatably connect said tool to a driving member. a plurality of superimposed convolutions secured on said shank. layers of abrasive material between adjacent convolutions. and means for releasably clamping said convolutions together.

9. A lapping tool comprising a shank, a helical coil on the end of said shank. successive turns of said coil having peripheral surfaces in alignment with each other, abrasive material between adjacent sides of. said turns and exposed at the outer periphery of said coil, and means for compressing said coil to provide. a substantial continuous working surface on the outer periphery thereof.

10. A lapping tool comprising a support, a stem on said support. a resilient member coiled about said stem, :1 film of diamond dust located between adjacent turns of said coil, and releasable means on said stem for retaining said resilient member under compression so as to confine said diamond dust between said convolution and to form a substantially continuous working surface on said coil.

CONRAD F. BIRGBAUER. 

